Numerical Study On The Flow Fields In Cyclone Separators Based On The Similarity Analytical Method

Gas/solid cyclone separators are widely applied in many industrial applications such as oil processing,coal-fired power generation and air pollution control.Former researchers have done extensive studies improving the separation performance.However,due to the limitation of their lab conditions,most of the previous research results could not cover the range of actual fields operations.On the other hand,many simplifications are raised when introducing similarity analysis to the design of cyclone separator,which limits the corresponding design accuracy.Based on the similarity analysis,this paper numerically studied the flow conditions inside the PV cyclone and a new type of modified cyclone with high efficiency and low resistance.The main conclusions are as follows:(1)For PV cyclone separator,the profile of the dimensionless tangential velocity and axial velocity almost maintain unchanged when the inlet velocity,temperature and the body diameter are increased.However,the profile of the dimensionless radial velocity develops irregularly,whose distribution is approximately origin symmetrical.On the other hand,the current model is modified by introducing in the Froude number Fr,a better prediction for the pressure of the PV cyclone separator is approached.(2)Based on PV cyclone,a new type of cyclone separator is designed for higher efficiency and lower resistance.The entrance structure is changed,the height of the separator cylinder is extended,a kind of split-flow gas exit tube with slots is applied.The cone-shaped transition section in the dustin is chosen.When creating the model,it needs to consider the influence of wall thickness and slots.Therefore,it increases the modeling requirements and difficulties in a new cyclone separator.(3)The distribution of the flow velocity inside the new cyclone is similar with that inside the PV cyclone.Both of the velocity profiles show upward internal vortex and downward outer vortex.In comparison to the PV cyclone,the intensities of the vortexes inside the new cyclone are greatly reduced and the stabilities of vortexes are slightly reduced.While both of the vortex symmetry and the natural vortex length are increased.The decaying speed of the vortex intensity along the axil is decreased.When the new gas exit tube is applied,an amount of gas gets inside the core tube through the slots.Correspondingly,the flow pattern inside the core tube is influenced.Such mutual influence causes the direction of gas swirl inside to be opposite to the outside.(4)With the increasing of the inlet velocities and structure sizes,the distribution of dimensionless tangential velocity and dimensionless axial velocity in the new cyclone remain nearly unchanged.In areas close to the core tube,the distribution pattern is unstable resulting from the influence of gas flow around the slots.The distribution of dimensionless radial velocity is relatively complicated with no regularity,which can be only regarded as origin symmetry.(5)When analysing the pressure drop of the new type of the cyclone separator,the Froude number Fr is introduced in the equation and the predicting accuracy is improved.The modification provides more scientific and reliable guidance for the design of prototype.The pressure drop curve of the new cyclone keeps well with the PV model,which proves that the Froude number Fr makes sense.